An example of an existing miniature electromagnetic relay is shown in FIG. 19. This relay consists of a box-shaped base 2, an electromagnetic block 4, a movable block 6, and a box-shaped case 7. Base 2 has a number of terminals molded onto it: common terminal 1a, fixed contact terminals 1b, and coil terminals 1c. Permanent magnet 3b is held in place by U-shaped iron core 3a. Coil 3d is wound around molded bobbin 3c, and the ends of the coil are tied and welded to studs 3f on lug terminal strips 3e. The bobbin is then mounted onto the base. Electromagnetic block 4 is formed as an integral unit by welding the lug terminal strips 3e to connection points 1d on coil terminals 1c located on the bottom of box-shaped base 2. (The connection point on the front of the base is not shown.) Electromagnetic block 4 is joined with support member 5c which supports movable contactors 5b at their centers. The movable contactors are disposed lengthwise along either side of movable armature 5a. Movable block 6 is formed as an integral unit by welding connectors 5d, which are formed as extensions from the centers of movable contactors 5b, to connection points 1e on common terminal 1a. Box-shaped case 7 has dimensions such that it can engage with the box-shaped base 2. The electromagnetic relay described above has a number of disadvantages.
In the electromagnetic relay described above, connectors 5d on movable block 6 are welded to connection points 1e. The welding process is essential, and since working space must be provided in and around the welding points, it is difficult to reduce the size of the device.
If the relay is to be made smaller, the welding points must be made smaller, which makes the task of welding significantly more difficult, and reduces production efficiency.
Another disadvantage of the electromagnetic relay described above is that because impurities such as carbon are generated during the welding process, a defective contact may occur. Also, variations in the welding process may lead to aberrations in the operating characteristics.
Further, since the relay described above has four independent structural components, it requires a large number of components and a large number of assembly processes. This makes it more difficult to manage the production process, and has an adverse effect on the precision with which the components are assembled.